Printed circuit boards have long been utilized for supporting and interconnecting electronic circuit components. Printed circuit boards are herein after referred to as "PC boards". Typically printed circuit boards are manufactured through a process in which a circuit pattern is delineated by using a photoresist on the face of a preformed insulating sheet having a metal surface bonded thereto. The portion of the metal surface which is not covered by the photoresist pattern is subsequently etched away to yield the desired conductive pattern on the insulating surface.
While integrated circuits have recently come into widespread use, printed circuit boards are still utilized extensively. It is usually necessary to physically support and interconnect a plurality of so-called IC chips with other discrete electronic components. Furthermore, many electronic circuits are not subject to miniaturization, for example power supplies and filtering circuits. These circuits consist of many discrete components which must be supported and interconnected on a printed circuit board.
The conventional method of producing printed circuit boards described above requires the steps of (1) covering the entire surface of the insulative board with a layer of conductive material, (2) applying a negative or reverse image of the conductive pattern using photoresist, and (3) etching away the excess conductive material with suitable etching agents. Clearly where thousands and even millions of units of a particular printed circuit board are to be produced, it is desirable from an economic standpoint to reduce the total number of steps in the manufacturing process. Furthermore, it is likewise desirable to reduce the quantity of materials required to produce the boards. The conventional method described above, when implemented on a large scale, results in the wastage of large amounts of conductive material, photoresist, and etching solution unless suitable means for recycling these materials are utilized.